The invention relates generally to the field of braided devices and more particularly to a braided devices having multiple filament types.
Braiding is used in a wide variety of different fields, for example, textiles, electronics, aerospace, and medicine, for performing a variety of different applications, for example, harnessing, shielding, and/or reinforcing, materials and structures, requiring special or high performance properties, characteristics, and behavior. In medicine, braiding is used to produce, among others, implantable intraluminal devices, including stents, stent-grafts, preventing devices and stroke preventing devices. Stents are used to support diseased or damaged arteries and body lumens, an example of which is disclosed in U.S. Pat. No. 4,655,771 issued to Wallsten whose contents are incorporated herein by reference, while stent-grafts have the added task of covering or bridging leaks or dissections. A stroke preventing device, also known as a diverter, is described in U.S. Pat. No. 6,348,063 issued to Yodfat et al., copending U.S. patent application Ser. No. 09/637,287 filed Aug. 11, 2000 entitled “Implantable Stroke Treating Device”, and co-pending U.S. Patent Application 10/311,876 filed Jul. 9, 2001 entitled “Implantable Braided Stroke Preventing Device and Method of Manufacturing” the entire contents of which are incorporated herein by reference.
Stroke preventing devices such as diverters, are typically produced from filaments comprising a finer wire than is found in a stent, as its task is primarily to filter, or block the flow of emboli, and not to support diseased or damaged arteries and body lumens. Unfortunately, in certain circumstances, filaments that are advantageous for use as a filter are insufficient to supply sufficient overall structural strength for the device. In other cases, fine wire filaments used in the device are not readily visualized under standard fluoroscopic equipment, thus rendering precise placement and follow up of patients difficult.
The term filament as used herein is to be understood to include strands, round wires, non-round wires, monofilaments, slit tape, multifilament yarn, braids or other longitudinal product.
In order for the implantable intraluminal device to be radiopaque, it must be made from a material possessing radiographic density higher than the surrounding host tissue, while having sufficient thickness to affect the transmission of x-rays and thus produce contrast in the image. A braided device, utilizing a biocompatible fine wire such as stainless steel or cobalt based alloys of a diameter less than 100 μm, such as a stroke preventing device described in pending U.S. patent application Ser. No. 10/311,876 filed Jul. 9, 2001 entitled “Implantable Braided Stroke Preventing Device and Method of Manufacturing”, whose contents are incorporated herein by reference is not normally radiopaque.
U.S. Pat. No. 5,718,159 issued to Thompson, incorporated herein by reference, discloses a process for making a prosthesis for intraluminal implantation, the prosthesis having a flexible tubular three dimensional braided structure of metal or polymeric monofilaments, and polymeric multifilament yarns. The monofilaments are selectively shaped before their interbraiding with the multifilament yarns, and the textile strands are braided in one or more layers of sheeting that reduce permeability. The use of a three dimensional braided structure, comprising pre-shaping of the monofilaments, adds extra complexity to the manufacturing process, with a resultant increase in cost.
The term two dimensional braided structure as used herein defines a braided structure comprising a single braid layer. The term three dimensional braided structure as used herein defines a braided structure comprising a plurality of braid layers.
Thus there is a need for a braided device comprising multiple filament types having improved structural stability. There is a further need for a method of braiding a braided device comprising multiple filament types, having improved overall structural stability.